Completely overriding the stock isolinux configuration

[Zack Weinberg <zackw@panix.com>]

Suppose I want to wipe out the entire stock isolinux configuration and
replace it with something along the lines of

default live-@FLAVOUR@ auto
prompt 0
noescape 1

label live-@FLAVOUR@
    linux @LINUX@
    initrd @INITRD@
    append @APPEND_LIVE@ noeject

... how would I accomplish this?  Putting that in
config/includes.binary/isolinux/isolinux.cfg.in causes it to be copied
verbatim to binary/isolinux, which doesn't accomplish anything useful.

Thanks,
zw